Particle system: hide dupli object
While you can't 'hide' the object used to render the particles you can make it invisible by setting it's material to be transparent.

For non-meta objects you can use the Particle Info node to detect which 'objects' are particles and use this to mix between the actual shader and a transparent shader to 'hide' the 'original' object - eg, by using a math Greater Than node to distinguish between those particles with a Lifetime greater than 0 (the particles) and that with Lifetime of zero (the 'original' object).

For Meta objects this is difference since the whole collection of particles and the 'original' object is rendered as a single combined surface so the Particle Info node is not applicable. In this case you can use the location of each rendered point to determine whether to render that surface or not. For example, positioning the 'original' object above the particle system you can use the Object texture coordinates to make the object transparent while leaving the particles rendered :



Adjust the Greater Than node so that the original object is hidden but the particles are not.